The invention relates to an electric lighter for lighting cigars or cigarettes, the lighter including a lighter Plug and a socket, and having a switch contact for connecting the lighter plugs to a terminal, and a means for temperature controlled opening of the switch contact.
Such a cigar lighter is known from U.S. Pat. No. 2,637,799. In this patent, a frequently employed cigar lighter for motor vehicles is described as prior art. Such a cigar lighter comprises a socket which is arranged in the dashboard of a motor vehicle and into which is inserted a lighter plug which contains a glow coil, as well as a negative pole which in vehicles is connected to a ground, the negative pole being connected to the lighter plug via a plug-in contact. When the lighter is to be heated, a connection to a positive pole is established via a movable part in the lighter plug, with the result that a current flows in the glow coil. The glow coil heats a bimetal spring which is arranged in the socket and releases the movable part of the lighter plug for the purpose of resetting it to a rest position and thereby switching off the current circuit when the lighter has heated up. Resetting is effected by a spring which was pre-tensioned when the current circuit was previously closed.
In the aforementioned patent, a design of a cigar lighter is taught which has fewer components as compared with previous lighters. In this design, illustrated in the drawings of U.S. Pat. No. 2,637,799 described above, the function of a resetting spring and of a trigger function of a bimetal spring are combined in one component, namely a bimetallic snap-action disc. However, this cigar lighter still has a relatively large number of components and requires a relatively high expenditure on production thereof. Further, the overall length of the lighter is relatively great. This results because a switch contact for the positive pole and a plug-in contact for the positive pole are arranged one behind the other. It is furthermore disadvantageous that the glow coil is a relatively long way away from the bimetallic snap-action disc, with the result that switching off does not occur exactly at a particular temperature but is dependent, for example, also on the ambient temperature.
In the aforementioned patent, the plug-in contact for the positive pole is formed by a glow-coil dish of the lighter plug and bimetal springs which are arranged in a bottom zone of the socket. This means that, each time the lighter plug is used, the glow-coil dish rubs against the contact springs of the socket and, as a result, is subject to wear. It is furthermore disadvantageous that the contact springs must be matched to the shape of the glow-coil dish. This is disadvantageous particularly because the socket of the cigar lighter is frequently used in vehicles for connecting accessory devices such as, for example, a lamp or a tool. The connection of accessory devices is effected via an accessory plug, the shape of which is approximately that of a lighter plug. There is the risk that, with accessory plugs, the contact springs in the socket will be bent. The same problem exists in the known design, described first in the above, having a bimetal spring. In addition, in both of the above-discussed types of design the contact springs of the positive pole are matched to the shape of the glow-coil dish, with the result that only small contacts are available. The conductor cross-sections and contact resistances at the points of contact which result from this construction limits the permissible current which can be drawn from the socket.